Periodic variations of waveguide transmission by use of rotating rutile loading member



N 8, 9 E. LINSENBARDT 3,284,729

A. PERIODIC VARIATIONS OF WAVEGUIDE TRANSMISSION BY USE OF ROTATING RUTILE LOADING MEMBER Filed May 28, 1964 ,IO Fig. I.

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WITNESSES 'NVENTOR Aldo E. Linsenbcmdr M m ATTORNEY United States Patent 3,284,729 PERIODHC VARHATIONS (1F WAVEGUIDE TRANS- MISSEGN BY USE OF RGTATING RUTILE LOAD- ENG MEMBER Aldo E. Linsenbardt, Catonsville, Mi, assignor to Westinghouse Electric Corporation, Pittsburgh, Pa, a corporation of Pennsylvania Filed May 28, 1964, Ser. No. 370,839 4 Claims. (Cl. 333-38) This invention in general relates to waveguides, and more in particular to means for controlling the propagation of microwave energy in the waveguides.

In many waveguide applications it is desirable to control the amount of microwave energy transmitted so that various couplings might be made to, for example, an output utilization device, or waveguide circuits having different characteristics. A device for reducing the microwave energy transmitted in the waveguide is generally termed an attenuator. In other waveguide applications it is often desirable to change the attenuation from a minimum loss to an effective short and in some applications to even reflect the microwave energy.

It is an object of the present invention to provide an improved device for controlling the propagation of microwave energy.

It is another object to provide a dielectric microwave switch which maybe utilized as a variable non-dissipative attenuator.

A further object is to provide a device for controlling the microwave energy within a wave-guide which device has extremely high power handling capability.

Yet another object is to provide a variable microwave attenuator which is of a relatively small size.

Briefly, in accordance with one embodiment of the present invention, there is provided a device for controlling the microwave energy in a waveguide and includes an element exhibiting an anisotropic or birefringent dielectric constant, positioned within the waveguide. The element exhibits a relatively high dielectric constant and a low impedance when positioned in a first orientation with respect to the electric field of the microwave energy, and exhibits a relatively lower dielectric constant and a high impedance when positioned in a second orientation. Means for positioning the element within the waveguide are provided so that the element may be selectively oriented with respect to the microwave energy. The above stated, and other objects will become more clearly apparent after a study of the following specification when read in connection with the accompanying drawings, in which:

FIGURE 1 is a side view of an attenuator element; and

FIGURE 2 illustrates the arrangement of an attenuator in accordance with an embodiment of the present invention.

FIGURE 1 illustrates an element exhibiting an isotropic dielectric constant and having first and second axes X and Y respectively. The element exhibits a first dielectric constant when one of the axes, for example the x axis which may be termed the main axis, is parallel to the electric field of the microwave energy within the waveguide. The element 10 exhibits a second and lower dielectric constant when the Y axis, which may be termed the minor axis, is positioned to be parallel to the electric field. In a preferred embodiment of the invention, the element 10 comprises rutile, which is titanium dioxide. Commercial rutile is generally flame grown at elevated temperatures of approximately 1200 C. and this material is capable of absorbing considerable microwave power as well as exhibiting a high dielectric constant.

Therefore, to control the microwave energy within a waveguide a relatively small element of rutile may be utilized and the means for positioning the element within the waveguide may be of low power requirements; to this end reference should now be made to FIGURE 2.

In FIGURE 2 there is shown a waveguide 12 having a bend therein, although it is to be understood that straight sections or other shapes of waveguides may be utilized. The rectangular waveguide 12 includes a side having a dimension of a and a width having a dimension of b. The rutile element 10 positioned within the waveguide has a cylindrical shape. In order to position the rutile element 10 relative to the electric field of the microwave energy within the waveguide 12, there is provided a substantially lossless rod 15 made of quartz or the like which extends through one side of the waveguide 12. Coupled to the rod 15 is driving means 17 which may be a low power motor, solenoid, or simply a knob adapted to be turned by hand so that the element 10 may be rotated in a plane perpendicular to the direction of propagation of the microwave energy. The rutile element 10 is preferably located centrally within the waveguide and means to properly support the rod 15 is provided and may take the form of a plastic foam block 20.

In operation, consider a situation wherein micro wave energy is propagated within the waveguide 12 such that the electric field is parallel to the a dimension of the Waveguide. A cylindrical rutile element 10 has its X, or major axis, parallel to the electric field and exhibits a low impedance to thereby allow propagation of the microwave energy. If the driving means 17 noW causes the rutile element to have its major axis parallel to the b dimension of the waveguide 12, the rutile exhibits a relatively higher impedance, maximum coupling occurs, an effective short is placed across the waveguide, and further propagation of the microwave energy is minimized. An effective attenuation of the microwave power intermediate these two positions may be achieved by positioning the rutile element 10 such that its major axis makes a predetermined angle between 0 and 90 with one of the dimensions of the waveguide 12 (and consequently with the electric field of the microwave energy). The rutile element 10 may be utilized to control the microwave energy and since the loss constant is extremely low the element 10 will be essentially non-dissipative.

Although a cylindrical rutile element 10 has been illustrated in the embodiment of the invention shown in FIGURE 2, it is to be understood that other shaped elements may be utilized. Essentially, the rutile element has a resonant frequency such that the above-described operation will take place when the frequency of the microwave energy in the waveguide is within a certain range. The frequency response of the rutile element basically is a [function of the element size and shape and it follows therefrom that other shapes of rutile elements may be utilized than that shown in FIGURE 2. To increase the range of frequencies at which desired control of the microwave energy in the waveguide may be obtained, several rutile pieces could be combined to give desired characteristics.

As an example of an operative system, a rutile element has been utilized in a waveguide carrying microwave energy at X-band frequencies. A rutile cylinder approximately 0.120 inch in diameter and 0.200 inch long was placed centrally within the X-lband waveguide and supported by a quartz rod cemented to the rutile element which in turn was supported by a foam block. The loss constant of the rutile element was in the order of 10 and the element exhibited a dielectric constant of approximately 170 in a first orientation and a relatively lower dielectric constant of 86 in a second orientation.

Although the present invention has been described with a certain degree of particularity, it should be understood that the present disclosure has been made 'by way of example. Other types of waveguides operating at other frequencies, other driving means, other means for supporting the rutile element within the waveguide and other modifications and variations of the present invention are made possible in light of the above teaching.

What is claimed is:

1. A switch for controlling the propagation of microwave energy within a waveguide comprising:

a rutile element having a known first dielectric constant when in a first orientation with said microwave energy and a known second, and lower dielectric constant when oriented 90 .from said first orientation; and

means for positioning said rutile element into said first orientation to allow propagation of said microwave energy and for positioning said element 90 therefrom to substantially minimize the propagation of said microwave energy.

2. A device for attenuating the microwave energy within a waveguide comprising:

a rutile element having a major and a minor axis;

said rutile element exhibiting a first known impedance when said major axis is parallel to the electric field of said microwave energy, and a second known impedance when perpendicular thereto; and

means for positioning said element relative to said electric field to allow propagation of said microwave energy when said first known impedance is presented to said energy and to minimize propagation of said microwave energy when said second known impedance is presented to said energy.

4 3. Apparatus for controlling the microwave energy within a waveguide comprising:

a rutile element having a first and second axis and positioned within said waveguide;

said rutile element exhibiting a known first dielectric constant when said first axis is positioned in a first orientation relative to the electric field of said microwave energy and a known second dielectric constant when positioned in a second orientation relative thereto;

'drive means located exterior to said waveguide; and

means coupling said rutile element to said drive means for positioning said axis relative to said electric field to allow propagation of said microwave energy when said rutile element is in said first orientation, to minimize propagation of said microwave energy when said rutile element is in said second orientation, and to attenuate said microwave energy when said rutile element is positioned intermediate said first and second orientations.

4. Apparatus according to claim 3 wherein:

the drive means rotates the rutile element in a plane perpendicular to the direction of the propagation of said microwave energy.

References Cited by the Examiner UNITED STATES PATENTS 8/1955 Allen 3333l OTHER REFERENCES HERMAN KARL SAALBACH, Primary Examiner. L. ALLAHUT, Assistant Examiner. 

1. A SWITCH FOR CONTROLLING THE PROPAGATION OF MICROWAVE ENERGY WITHIN A WAVEGUIDE COMPRISING: A RUTILE ELEMENT HAVING A KNOWN FIRST DIELECTRIC CONSTANT WHEN IN A FIRST ORIENTATION WITH SAID MICROWAVE ENERGY AND A KNOWN SECOND, AND LOWER DIELECTRIC CONSTANT WHEN ORIENTED 90* FROM SAID FIRST ORIENTATION; AND MEANS FOR POSITIONING SAID RUTILE ELEMENT INTO SAID FIRST ORIENTATION TO ALLOW PROPAGATION OF SAID MICROWAVE ENERGY AND FOR POSITIONING SAID ELEMENT 90* THEREFROM TO SUBSTANTIALLY MINIMIZE THE PROPAGATION OF SAID MICROWAVE ENERGY. 